82 Evinrude loses power under load

[dfgtye]

Hello everyone. Just ran into this today. Put a good running 1982 Evinrude 25 on a pontoon barge I use for moving things back and forth between an island and shored. Started right up runs good. Took for a test run and everything worked great. Docked it for about an hour. Started up in one crank. Motored out about 100 yards and it started bogging down and losing power. Limped back to the dock. Runs perfect at idle. I can rev it all the way up , out of gear. Nothing in the prop. Plenty of new fuel. New oil in the lower unit before I put it on the boat. Checked compression when I pulled it out of the garage before I put it on. Nothing seems to be obstructing the carb. Any Ideas?? The confusing part is that it was running perfect , then just changed, like something is restricting. The gas flow, but it runs fine out of gear. Doesn't change if I add choke.

 

[interalian]

You could have lost spark on one cylinder. Do a cylinder drop test with insulated pliers - when running, pull one plug wire and see what happens to the speed, then put it back and try the other. If only one affects it, that's the one that's working. And don't rev the whee out of it in neutral, or BANG!

 

[dfgtye]

Checked the plugs. Getting spark in both cylinders. The engine will run on either one at idle. Also just tried it in reverse. No issue. I can accelerate in reverse no problem. I think this rules out spark and carb.

 

[interalian]

If it were mine, I'd do a high-speed cut and read the spark plugs when it's misbehaving. How's your compression?

 

[oldboat1]

Clue to me is that choking has no effect. I think the motor should stall if choked when warmed up and running. Will guess that maybe the choke plate is stuck partially closed, and engine is bogging above idle (too rich). Maybe the linkage or solenoid. I would see if the choke plate is fully opening and closing properly.

[edit. See it revs in neutral, though -- shoots a hole in the choke plate theory.]

 

[dfgtye]

Choke is working fine. If I use the choke, or put my hand over the opening, the engine will stall out. Could this be something in the gear box/lower unit. It doesn't just bog it surges as well . Didn't note this before. It is not slipping in gear, not the clutch dog . It is staying in gear . Just really feels like something is holding it back, like it's got seaweed wrapped around the prop ( I checked, it doesn't)

 

[dfgtye]

Just ran it without the prop. Revs just as it should. Totally an issue under load.

 

[oldboat1]

slipping prop hub, possibly.

 

[ondarvr]

What it does in neutral means nothing, they can sound great running on just one cylinder. Start checking stuff, pull off plug wires etc. you said the carb is unobstructed, did you clean it?

 

[dfgtye]

Carb was cleaned last season. The engine ran and worked perfect earlier today. Issue came on suddenly. Pulled each wire while running, both cylinders are getting spark. The engine will run on either one separately. Checked all connections. Everything is good and tight. No breaks in any wires or wear spots. Disconnected and reconnected all plug in fittings.

 

[ondarvr]

Having a carb clean last year, or even this morning doesn't mean it's clean now, when it plugs up, it plugs up. Not saying that's what it is, just a possiblity.

Pull a plug wire and then try to run the boat at speed, see if spark fails one cylinder under load.

 

[Gary H NC]

What about your fuel primer bulb? Any signs of it sucking shut when the motor bogs down?
Possibly try another portable fuel tank....rule that out as a problem then work to the fuel pump and carb..
I would pull the carb and clean it again just to be safe...

I do all 3 of my carbs every year...no big deal and you can see if any crud is in the float bowl.

Rule out any fuel starvation possibility first before throwing parts at it.

 

[jakedaawg]

If it runs fine in reverse but not in forward you have your answer. Drain lower and see what comes ou .